Is Door-to-Balloon Time a Misleading Metric?

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Door-to-balloon time is an integral process metric for measuring cardiovascular quality. Since its inclusion in the ACC/AHA Guidelines for STEMI management as a Class 1A recommendation,1 door-to-balloon time has evolved into a national quality metric. CMS began publicly reporting this measure, and subsequently hospital performance on door-to-balloon time was tied to financial reimbursement. As a result, there has been considerable emphasis on improving hospital performance on this metric, which has changed not only the practice of cardiology, but also the coordination of health care delivery in acute care settings. However, as cardiovascular care has evolved, it becomes important to pause and consider whether door-to-balloon time as a metric in current practice has become misleading.

Door to balloon time is an important cardiovascular process measure because it is both clinically meaningful and actionable. On a patient level, door-to-balloon time directly correlates with an amount of time the myocardium undergoes ischemic damage. Intuitively, reducing such time should reduce the degree of ischemic damage and ultimately improve patient outcomes. Indeed, in observational studies, shorter door-to-balloon times for individual patients are associated with lower mortality in-hospital,2-4 at 30-days,5 and at 1 year.6

From a systems point of view, door-to-balloon time is an actionable measure. It has a clearly defined start point and end point, making it a specific and measurable target for improvement. In contrast to demographic and clinical characteristics known to affect patient outcomes, door-to-balloon time is a risk factor that is clearly modifiable by healthcare providers. Furthermore, there was considerable variation across institutions around the time of its adoption as a standardized quality metric,7 allowing lower performing hospitals room for improvement and opportunities to learn from top performing hospitals.8-10

Since the widespread adoption of door-to-balloon time as a measure, there have been many changes in practice patterns. The ACC launched the D2B Alliance in 2006 to promote strategies to increase the percentage of patients with door-to-balloon times within 90 minutes11, which was regarded as achieving its aim.12 Nationally, door-to-balloon time declined from a median of 96 minutes in 2005 to a median of 64 minutes in 2010.13 In fact, door-to-balloon time as a measure was recently considered by CMS to be 'topped out,' meaning that there was minimal distinguishable variation in performance between hospitals. As such, door-to-balloon time will still be publicly reported, but it will no longer be a metric used to calculate financial payment.

Given these changes in practice, it becomes important to critically re-evaluate the value of door-to-balloon time as a modern metric. Upon closer inspection, population-wide door-to-balloon time may not have improved as much as the CMS-reported metric has demonstrated. While median door-to-balloon time has decreased, new evidence suggests that the number of cases excluded from CMS-reported measures has increased over time.14 Such cases tend to be longer and in more complicated patients, those who may benefit the most from a reduced door-to-balloon time. Empirically, those excluded have much worse outcomes at one year. Taken together, this suggests that the current metric, as measured, may be less useful than one which more comprehensively captures patients with STEMI.

An emphasis on door-to-balloon time as a metric must be met with evidence that improvements in this metric lead to improvements in outcomes. While longer door-to-balloon time is associated with worse outcomes,2-6 it is unclear whether improvements in door-to-balloon time as a metric can cause improved health outcomes. A longitudinal analysis from the ACC's National Cardiovascular Data Registry showed that, while door-to-balloon times had decreased significantly between 2005 and 2009, overall in-hospital or 30-day mortality did not decrease during this same period.16 However, re-analysis of the same data between 2005 and 2011 found a continued association between shorter patient-specific door-to-balloon time and lower mortality despite population-wide trends towards increased mortality.17 Taken together, these studies suggest that changes in the primary PCI population over time could account for the population trend towards increased mortality, though patients with longer door-to-balloon time may have been sicker in unmeasurable ways that were unaccounted for in risk adjustment. Further research is needed to elucidate the causal effect of improving door-to-balloon times on patient outcomes. Additionally, while door-to-balloon time is important, it represents only a fraction of overall ischemic time, and emphasis on this metric should be made in concert with other efforts to improve cardiovascular care.

Furthermore, the emphasis on improved door-to-balloon time as a metric can lead to unintended consequences if not considered appropriately. A focus on improving door-to-balloon time can lead to greater potential for incomplete evaluation in the emergency room and subsequent catheterization of poor PCI candidates or missing of alternative diagnoses, ultimately leading to worse outcomes. In addition to potential adverse effects on an individual level, there is greater potential for unnecessary catheterization, which can lead to increased system-wide resource utilization. One study found that between 14-36% of all emergency department-activated catheterizations for suspected STEMI were 'false positive' activations.18 Further attention to patient-level characteristics associated with such false positive activations must be given while emphasizing improvement in door-to-balloon time.19

Additionally, inordinate focus on this metric may stifle further innovation in PCI for STEMI. This is evident in the uptake of trans-radial procedures for STEMI. Overall, the trans-radial approach has improved outcomes compared to the trans-femoral approach among experienced operators.20 Utilization of the trans-radial approach for STEMI has skyrocketed in recent years with six-times as many procedures being done radially in 2011 compared to 2007.21 However, the absolute percentage of cases performed radially in 2011 was still very low at 6%. Interventional cardiologists commonly cite concerns of not achieving adequate door-to-balloon times as a primary reason to avoid the transradial approach in STEMI patients, despite robust data demonstrating improved patient outcomes with this approach. However, we have shown that, even accounting for the potential for greater ischemia associated with a longer door to balloon time, one would still expect better outcomes through the trans-radial approach compared to the trans-femoral approach.22 In this case, physicians' desires to meet a performance metric may in fact be leading to worse quality of care.

Ultimately, incredible progress has been made in the coordination of care as a result of emphasis on improving door-to-balloon time. Nevertheless, door-to-balloon time, as currently reported to CMS is not a complete reflection of quality of STEMI care, and there may still be room for improvement. Further research is necessary to elucidate the true benefits of further improving door-to-balloon-time on patient outcomes in practice. Continued emphasis on improving performance on this metric must take into account both the potential benefits as well as unintended consequences of such actions for patient outcomes.

References

Antman EM, Anbe DT, Armstrong PW, et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Revise the 1999 Guidelines for the Management of Patients with Acute Myocardial Infarction). Circulation 2004;110:e82-292.

McNamara RL, Wang Y, Herrin J, et al. Effect of door-to-balloon time on mortality in patients with ST-segment elevation myocardial infarction. Journal of the American College of Cardiology 2006;47:2180-6.

McNamara RL, Herrin J, Bradley EH, et al. Hospital improvement in time to reperfusion in patients with acute myocardial infarction, 1999 to 2002. Journal of the American College of Cardiology 2006;47:45-51.

Bradley EH, Roumanis SA, Radford MJ, et al. Achieving door-to-balloon times that meet quality guidelines: how do successful hospitals do it? Journal of the American College of Cardiology 2005;46:1236-41.

Baklanov DV, Kaltenbach LA, Marso SP, et al. The prevalence and outcomes of transradial percutaneous coronary intervention for ST-segment elevation myocardial infarction: analysis from the National Cardiovascular Data Registry (2007 to 2011). Journal of the American College of Cardiology 2013;61:420-6.